Judging by what information is currently available though, I really can't see a way how they could do that.I'm sure they'll have something sorted for when away teams don't take their full allocation as well, though might be a little trickier as the lower part is standing and then above the wheelchair access it's seating. I'm sure they'll find a way though.
Area in green is the Away end Safe Standing, and the red is Away end Seating. It looks like both of these sections share the only 3 entranceways (and concourse) in the Away end. You couldn't have home and away fans sharing the same concourse / steps, there'd be carnage
(cheers to @phil_t98 for the vid)